Why would you feel bad? The whole point of open source is they could have done it themselves, if they wanted some integration they needed and you didn't.
And then they could either contribute it back, fork your project or just keep it to themselves, if the license allows it. At any rate, you already helped them...
And then they could either contribute it back, fork your project or just keep it to themselves, if the license allows it. At any rate, you already helped them...